1. Field of the Invention
The present invention relates to a printing system including a plurality of processors performing a conversion process from a page description language format of data into raster image data, and a printing engine which continuously receives color image data having at least three color components in page unit and prints the at least three color components of color image data on a recording medium in parallel at a constant speed.
2. Description of the Related Art
Ink-jet and electro-photography color printers are becoming commonplace in recent years. Particularly, with electro-photography color laser printers, photosensitive drums are provided for each of the four colors of cyan, magenta, yellow, and black, color image data (color image data of the four colors, CMYK) is received from a host computer in increments of pages, and the color image data of the four colors is recorded on recording sheets almost simultaneously (in a parallel manner) at a constant speed. Such electro-photography color laser printers are generally called page printers, since image data is received in increments of pages, and the image data of the received one page is recorded at a constant speed. With such page printers, data in the format of what is generally called a Page Description Language such as PostScript (PS) or Printer Control Language (PCL) is received from a host computer, and the data in the Page Description Language format received by the page printer is rendered as Raster Image Data (i.e., rasterized) and recorded in increments of pages.
With conventional color printers, the processing for rasterizing consumes time in the case of Page Description Language format data containing color image data, with color image data containing large amounts of raw data in particular. Conventional rasterizing processing of Page Description Language format data has been a sequential process in increments of pages wherein at the point that the rasterizing processing for one page is completed, the flow moves to the rasterizing processing for the next page, so the recording of that page cannot be performed until the rasterizing processing for that page is completed and the color raster image data for that page is prepared, and meanwhile the printer is set to a standby state until the recording data is prepared, so consequently there has been a problem in that multiple pages of image recording cannot be performed at high speed in a continuous manner. Particularly, in the case of color page printers using photosensitive drums for the four colors of CMYK as described above, even though the printer might have capabilities for recording multiple pages of color image data at high speed in a continuous manner, the rasterizing processing has been time-consuming, so the printer capabilities have not been fully utilized. With color page printers currently being provided to the market, a speed of 3 pages per minute (or PPM) is the limit in the event of recording multiple pages of color image data in a continuous manner. A faster PPM rate may be achieved using a high-capability processor with a faster processing speed to increase the speed of the above rasterizing processing, but such high-speed processors are expensive, and this would consequently make the price of the printer very expensive.
Also, an arrangement is disclosed in U.S. Pat. No. 5,652,711, wherein, in the event of rasterizing Page Description Language format data, two sub-processors are used for executing translation processing of the data in increments of data stream segments, the data subjected to translation processing by the two sub-processors is synthesized so as to configure an intermediate data stream, following which the intermediate data stream is converted into bit map data, thereby increasing the speed of the rasterizing processing. However, the processing disclosed in U.S. Pat. No. 5,652,711 also performs sequential processing in increments of pages wherein the rasterizing processing for one page is completed and then the flow moves to the rasterizing processing of the next page, so in the event that color image data requiring time for the rasterizing processing is included partway through, the page printer goes on standby until the rasterizing processing for that page is completed, the same as with the above. Further, U.S. Pat. No. 5,652,711 makes no description whatsoever regarding increasing the speed of rasterizing processing for Page Description Language format data containing color image data.